A machine of the aforementioned kind is known from DE 2061422 A1. This machine, which is a mixing machine, is utilized in the foundry industry for mixing water, sand and a binding agent into a viscous mass of molding sand. Here a central shaft rotates a set of rollers operating interactively with a stationary table which is configured as a container to prevent outflow of water from the container. This is a discontinuous process which means that after the material on the table has been finally mixed, it will be necessary to stop the mixing machine to remove the material before a new quantity of water, sand and binding agent can be added. Timewise it is a distinct problem that the machine has to be stopped, and the removal of the material is also a labour-intensive process.
Furthermore, roller mills are generally known in the cement manufacturing industry and they are extensively described in the patent literature. Hence, from GB 2100617 A is known a roller mill with a number of rollers operating interactively with a horizontally rotating grinding table to which raw material continuously is fed. The rollers have stationary roller shafts and therefore they are not rotatable relative to a vertical axis. The rollers are forced against the grinding table by means of external spring-supported force mechanisms, for example in the form of hydraulic or mechanical springs. In this roller mill the grinding table is surrounded by a nozzle ring and through this nozzle ring a gas flow passes, being generated by a fan, with entrainment of the material discharged from the rotating grinding table which is very finely ground. This provides for a continuous grinding process due to the fact that the ground material is continuously removed from the grinding table while at the same time fresh raw material is fed to the center of the grinding table. In this type of mill, rotation of the grinding table is a specific requirement to ensure that the centrifugal force thus produced will force material fed to the center of the grinding table outward to the rollers and from there onward to the edge of the table from which the gas flow through the nozzle ring continues the transport of the material, normally to a separator. All roller mills of this type are characterized in that a mutually limiting interaction exists between the diameter of the grinding table and the rotational speed of the grinding table and in that they depend upon the permissible size of the centrifugal field as determined by experience. This is a significant disadvantage since it makes it impossible to increase the capacity of the roller mill by increasing the rotational speed of the grinding table and the diameter of the grinding table after the interrelationship between them has reached a certain level. The following formula for the maximum interrelationship between the rotational speed of the grinding table and the diameter of the grinding table applies for this type of roller mill:ω=K/D0.5                 where,        ω=rotational speed of the table [rad/s]        K=constant which is experimentally determined and dependent on the roller mill design and the nature of grinding material [m0.5/s]        D=the diameter of the table [m]        
As a consequence hereof, for roller mills with rotating tables where the upper limits for table speed and table diameter have been reached it will only be possible to increase the capacity by increasing the grinding pressure. Increasing the grinding pressure is not desirable for several reasons, i.a. because it will increase the stress loads imposed on the roller mill components, hence calling for greater strength characteristics of these components. The need to comply with the aforementioned formula is thus a problem if the capacity of the roller mill is to be increased. In case of non-compliance with the formula, the roller mill vibrations will reach a level which is so high that it will not be possible to achieve satisfactory operating conditions. Also, a higher vibration level will increase the requirements applying in terms of the mechanical strength of the roller mill components. Therefore, it is a well-known fact in the industry that compliance with the mentioned formula, or similar formulae, for the interrelationship between the grinding table diameter and grinding table speed must be ensured, and all roller mills of this type in operation today comply with the mentioned formula or similar formulae.